EP1797702A1

EP1797702A1 - Communications network

Info

Publication number: EP1797702A1
Application number: EP05775942A
Authority: EP
Inventors: Karl Bittnar; Arno-Gert Fabritius; Viktor Karell; Klaus Kirchberger
Original assignee: Siemens AG
Current assignee: Unify GmbH and Co KG
Priority date: 2004-10-05
Filing date: 2005-08-18
Publication date: 2007-06-20
Anticipated expiration: 2025-08-18
Also published as: US8339937B2; GB2419059A; CN101036377B; GB0422005D0; CN101036377A; EP1797702B1; WO2006037400A1; US20080304478A1

Abstract

A distributed Internet Protocol (IP) communications network comprises a central control system comprising control processing means and at least one access point remote from the central control system for providing access to the packet based communications network. Under normal operating conditions the at least one access point is controlled by the control processing means. The network also comprises an emergency processing means distinct from the central control system for contolling the least one access point when there is a failure in the control processing means control of the at least one access point.

Description

Communications Network

The present invention relates to a communications network.

In the past, large companies having a corporate headquarters and multiple branch offices have tended to operate independent self-contained telecommunication systems at each of the branches and at the headquarters. Naturally, these independent systems would be networked together. The administrative effort and the costs involved in running such multiple independent systems was high.

More recently, by using Internet Protocol (IP) internetworking between the headquarters and the various branches, it has been possible to relocate parts of the headquarters central system into the branches, whilst retaining a single point of control at the headquarters.

Systems based on the HiPath 4000 IP Distributed

Architecture, provided by Siemens AG, are examples of such IP internetworked systems. An example of a HiPath 4000 IP Distributed Architecture system is shown schematically in Figure 1.

Telecommunication system 1 comprises a first Local Area Network (LAN) 2 located at a company's headquarters, a second LAN 3 located at a first branch office (not shown) , a third LAN 4 located at a second branch office (not shown) and a fourth LAN 5 located at a third branch office (not shown) . The first LAN 2 is connected to a first router 6, the second LAN 3 to a second router 7 , the third LAN 4 to a third router 8 and the fourth LAN 5 to a fourth router 9. These routers connect the LANs via a Wide Area Network (WAN) 10.

A first access point 11 connects to the first Lan 2, a second access point 12 connects to the second LAN 3, a third access point 13 connects to the third LAN 4 and fourth 14 and fifth 15 access points connect to the fourth LAN 5. These access points 11 to 15 allow the connection of client terminals (not shown) to the LANs 2 to 5 and hence to the WAN 10. In a typical HiPath 4000 system the client terminals may either be traditional Time Divsion Multiplexed (TDM) devices, for example standard telephones or cordless telephones, or IP devices, for example IP telephones.

A central control system 16 connects to the first LAN 2 at the headquarters (not shown) and is responsible for controlling the operation of each of the access points 11 to 15. Each of the access points 11 to 15 comprises a respective gateway card 11a to 15a and a plurality of peripheral cards lib to 15b. The peripheral cards lib to 15b provide multiple peripheral ports for connection to client terminals, for example phones and/or trunk lines. The gateway cards 11a to 15a are the controllers of the IP based Access Point. Each of the cards 11a to 15a acts as a gateway between the LAN on one side of the card, and the client terminals on the other side of the card, converting payload data (e.g. voice data , fax data and ISDN-data) from TDM data to IP data and vice versa. Each of the cards 11a to 15a provides a local TDM switching matrix, conference units and tone generators. Each of the gateway cards 11a to 15a may be Siemens' HG 3575 cards.

The central control system 16 comprises a plurality of gateway cards 16a, a plurality of peripheral cards 16b, an administration and data processor 16c, a common control processor 16d and a back up common control processor 16e.

Again, the plurality of peripheral cards 16b provide multiple peripheral ports for connection to client terminals, for example phones and/or trunk lines. The gateways 16a translate payload data (voice/fax/ISDN-data) from TDM data on the client terminal side of the gateways to IP data on the LAN side of the gateways and vice versa. These gateways are used for connections between the IP based access points 11 to 15 and the central system 16. These cards 16a may be Siemens' HG 3570 cards.

The Administration and Data Processor 16c runs administrative software and applications, whilst the common control processor 16d runs call processing software. The back up common control processor 16e provides a back up to the common control processor 16d and in the event of the failure of the common control processor 16d, it can be switched into use without interrupting active calls.

The access points are controlled by the common control processor 16d. Every activity of the peripheral cards, for example, tones or displays at the phones and signaling messages at trunk interfaces are controlled by the common control processor 16d via a control link over the IP network. A complete set of administrative parameters in a database (not shown) in the central system 16 is kept in the memory of the control processor 16d. A persistent copy of the database is kept on hard disc which is controlled by the administration and data processor 16c.

Such systems have reduced administrative outlay but an increased dependence on the availability of the network and of the central system. If the central control fails, no further telecommunication is possible - in the corporate HQ or in the branches. A very high availability of the central control is achieved by duplicating the control processors.

As illustrated in Figure 2, in order to maintain control of access points upon failure of the WAN 10, a modem connection may be established between the central system 16 and some or all of the access points. In figure 2, a connection between the central system 16 and the third access point 13, the fourth acess point 14 and the fifth access point^' 15 is made through the Public Switched Telephone Network (PSTN) 17 via a router 18 connected to the LAN 2 and a first modem 19 connected to the gateway

13a, a second modem 20 connected to the gateway 14a and a third modem 21 connected to the gateway 15a. Access points without modem connections, in this example, the second access point 12, go out of service when their WAN connections fail. However, even back up systems such as this are useless in the event of total failure of the central system brought on by a catastrophy such as flooding or destruction of the building.

Embodiments of the present invention aim to alleviate the above described problems. According to the present invention there is provided a distributed packet based communications network comprising: a central control system comprising control processing means; at least one access point remote from the central control system, the at least one access point for providing access to the packet based communications network, wherein under normal operating conditions the at least one access point is controlled by the control processing means; and emergency processing means distinct from the central control system for controlling the at least one access point when there is a failure in the control processing means control of the at least one access point.

The above and further features of the invention are set forth with particularity in the appended claims and together with advantages thereof will become clearer from consideration of the following detailed description of an exemplary embodiment of the invention given with reference to the accompanying drawings, in which:

Figure 1 illustrates a communication system and has already been described;

Figure 2 illustrates a communication system and has already been described;

Figure 3 illustrates a communications system embodying the present invention.

Referring now to Figure 3 of the drawings, in which identical features as those illustrated in Figure 1 are given like reference numerals, a communications system 100 embodies the present invetion.

Under normal operating conditions the communications system 100 functions identically to the system 1 illustrated in Figure 1. That is to say, the four access points 11 to 15 are all operated under the central control of the central system 16.

The system 100 is provided with an emergency de-centralised control system for controlling access points in the event of the failure of the IP network linking access points and the central system 16 or if the central system 16 is not actually available. To this end, the first access point 11, the third access point 13 and the fourth access point 14 are provided with their own emergency control processors labelled lie, 13c and 14c respectively.

Each of the emergency control processors lie, 13c and 14c offer the same functionality as the central control. They possess the same software, the same patch status (i.e.software corrections applied to the system while running) and identical configuration data as do the administration and data processor 16c and the common control processor 16d of the central system 16. Groups of access points are assigned to emergency control groups, each emergency control group comprising one of the emergency control processors lie, 13c and 14c. In the system 100, the first access point 11 and the second access point 12 makeup a first emergency control group, the third access point 13 makes up a second emergency control group and, the fourth access point 14 and fifth access point 15 make up a third emergency control group. Each of the emergency control processors lie, 13c and 14c is in contact with the the gateway cards in its respective emergency group. Thus, if an access point of an emergency group loses contact with the central system the emergency processor of that group may take control of the access point.

A mechanism is provided for keeping the software status and the configuration data of the emergency control processors identical to that of the central system 16.

A backup server 22 is connected to the WAN 10, and in order to save on transmission bandwidth the software the software and database of the central system 16 is transmitted periodically, for example each day, to the backup server 22. This backup server 22 is as a general rule a separate device from the central system 16 and the emergency control processors lie, 13c and 14c. The central system 16 and all the emergency control processors lie, 13c and 14c have access via the IP network 10 to the backup server 22. The emergency control processors lie, 13c and 14c check cyclically whether updated data is present on the server 22 and download it where necessary. Thus each emergency control processor maintains an identical database to that at the central control . In an emergency the emergency control processors lie, 13c and 14c can thus behave in exactly the same way as the central system processors .

A fault occurs when an access point can no longer be served by the central control 16. If an access point gateway card detects a problem with the signalling connection between the access point of that card and the central system 16, it reports that fact to the emergency processor of the emergency group to which the access point belongs. The emergency processor decides according to preconfigured rules whether to take over control of the access point or not. In one embodiment, each access point in an emergency group is assigned a weight value of between zero and one, and when the total weight value of all access points in the emergegency group that have lost connection with the central system 16 equals or exceeds a predefined threshold, the emergency processor of the group takes over controll of those access points. So for example, in an emergency group comprising three access points each having a weight value of 0.5 and wherein the threshold is 1, it is only when at least two access points have reported a central system connection failure that the emergency processor steps in and assumes control of those access points. Naturally, an individual access point of particular importance, for example an access point serving the telephones of senior managers, may be assigned a weight value equal to the threshold value so that if this access point loses connection with the central system, an emergency processor immediately asssumes control of it.

In alternative embodiment, the access points in an emergency group may be configured to be taken over individually by the group's emergency processor as and when an access point loses contact with the central system 16.

Naturally, the access points may be configured so that an immediate hand over to an emergency processor may be ordered by the system administrator.

In a preferred embodiment, to take over control of an access point, the emergency processor instructs the gateway card of the access point to restart and to start up with the emergency processor.

If the central system 16 succedes in re-establishing a control connection to an Access Point in emergency operation, the access point remains under the control of the emergency processor but notifies it that it has re¬ established contact with the central system 16. The emergency processor decides in accordance with pre-defined rules whether and when emergency operation can be ended.

For example, emergency control may be ended only if every access point in an emergency group has had a stable connection with the central system 16 for a configurable pre-determined time period. Emergency control may only be ended at configurable pre-defined times of the day. The system may be configured so that a system administrator may order the end of emergency control .

To end emergency control of an access point, the emergency control processor instructs the gateway card of the access point to do a restart and to start up under the control of the central system 16.

Having thus described the present invention by reference to preferred embodiments it is to be well understood that the embodiments in question are exemplary only and that modifications and variations such as will occur to those possessed of appropriate knowledge and skills may be made without departure from the scope of the invention as set forth in the appended claims.

Claims

1. A distributed packet based communications network comprising: a central control system comprising control processing means; at least one access point remote from the central control system, the at least one access point for providing access to the packet based communications network, wherein under normal operating conditions the at least one access point is controlled by the control processing means; and emergency processing means distinct from the central control system for controlling the least one access point when there is a failure in the control processing means control of the at least one access point.

2. A system according to claim 1 comprising means for providing the emergency processing means with the same functionality as the control processing means.

3. A system according to claim 2 further comprising a server to which data from the central control system is uploaded for downloading to the emergency processing means for the emergency processing means to maintain the same functionality as the control processing means.

4. A system according to any preceding claim wherein upon detection of a failure in the control processing means control of the at least one access point, the emergency control processor determines whether to take control of the at least one access point in dependence upon predetermined rules.

5. A system according to any preceding claim wherein the at least one access point provides TDM user terminals access to the packet based communications network.

6. A system according to any preceding claim comprising a plurality of access points, which access points form a group of access points and wherein the emergency processing means is for controlling any of the access points in the group when there is a failure in the control processing means control of any of the access points in the group.

7. A system according to any preceding claim comprising a plurality of groups of access points, each group comprising one or more access points and an emergency processing means for controlling any of the one or more access points when there is a failure in the control processing means control of the any of the one or more access points.

8. A processing means arranged for use as an emergency processing means in the system of any of claims 1 to 7.

9. An access point comprising the processing means of claim 8 for use in the system of any of claims 1 to 7.